The James Webb Space Telescope (JWST) will be a large infrared telescope with a 6.5-meter primary mirror.

JWST will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own solar system.

JWST was formerly known as the Next Generation Space Telescope (NGST). JWST was renamed in Sept. 2002 after a former NASA administrator, James Webb.

JWST is an international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA). The NASA Goddard Space Flight Center is managing the development effort. The prime contractor is Northrop Grumman; the Space Telescope Science Institute will operate JWST after launch.

Several innovative technologies have been developed for JWST. These include a folding, segmented primary mirror, adjusted to shape after launch; ultra-lightweight beryllium optics; detectors able to record extremely weak signals, microshutters that enable programmable object selection for the spectrograph; and a cryocooler for cooling the mid-IR detectors to 7K. The long-lead items, such as the beryllium mirror segments and science instruments, are under construction.

There will be four science instruments on JWST: a near-infrared (IR) camera, a near-IR multi-object spectrograph, a mid-IR instrument, and a tunable filter imager. JWST's instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range. It will be sensitive to light from 0.6 to 27 micrometers in wavelength.

JWST has four main science themes: The End of the Dark Ages: First Light and Reionization, The Assembly of Galaxies, The Birth of Stars and Protoplanetary Systems, and Planetary Systems and the Origins of Life.